The majority of smokers are motivated to quit. However, most quit attempts end in failure, with many relapses occurring in the first few days. It is therefore important to understand the mechanisms underlying relapse to smoking, so that more effective interventions can be developed. Most research on the psychological processes underlying relapse has relied on questionnaire (self-report) measures to assess the relevant constructs. We shall utilize computerized reaction time tasks, derived from experimental cognitive psychology, to assess processes that may not be captured by self-report. Two-hundred and forty adult smokers wishing to quit will be enrolled in a smoking cessation study. All participants shall attend five laboratory sessions. At each session, they shall complete a battery of cognitive assessments (the modified Stroop task, the Implicit Association Test (IAT), and the Expectancy Accessibility Task (EA)). They shall complete these assessments at two pre-quit sessions, once when overnight deprived of smoking, and once when smoking normally. They shall also complete the assessments on their quit day, one week after their quit day, and at end of treatment (one month). During the treatment period, all participants shall be provided with individualized brief counseling. The over-arching goal of the proposed study is to evaluate the clinical and theoretical utility of the cognitive measures. The primary specific aim is to examine the associations between the cognitive measures assessed at the pre-quit sessions and subsequent smoking cessation outcomes. We hypothesize that smokers who exhibit greater attentional bias (Stroop task), more positive implicit evaluations of smoking (IAT) and stronger expectancy accessibility (EA Task) will be more likely to relapse to smoking. For each cognitive measure, we shall also examine whether any association with relapse: i) persists when controlling for self-report measures of relevant constructs, and: ii) is moderated by deprivation state at test. Smoking is an important public health problem costing over 430,000 lives a year in the US alone. This study will improve our understanding of the psychological processes underlying relapse to smoking. Thus, results from this study may help us to identify individuals who are high risk for an early relapse, and facilitate the development of smoking cessation interventions.